1. Field of the Invention
The present invention relates to an image obtainment method and apparatus for imaging an observation target by administering an agent to the observation target. Particularly, the present invention relates to an image obtainment method and apparatus for imaging the observation target to observe a temporal change in the image of the observation target.
2. Description of the Related Art
Conventionally, endoscope apparatuses that can observe tissue in the body cavities of patients are well known. Further, electronic endoscopes that obtain ordinary-images of observation targets in the body cavities by imaging the observation targets illuminated with white light and display the ordinary-images on monitors are widely used in medical fields (for example, please refer to Japanese Unexamined Patent Publication No. 2003-126014).
In such endoscope apparatuses, for example, a dye such as ICG (indrocyanine green), which absorbs light of a specific wavelength, is sprayed onto or injected into tissue in vivo, which is an observation target. Further, in some cases, a change in the absorption characteristic is observed in time series to observe the properties of the tissue, such as the form and texture of the tissue. This method is often used to observe the flow of lymph to the sentinel lymph node of a patient.
However, the temporal change in the absorption characteristic, the fluorescence characteristic or the like of the observation target by administration of the aforementioned agent is minute. Therefore, it is very difficult to recognize the temporal change only by macroscopically observing an ordinary-image displayed based on image signals obtained by an imaging device. Consequently, the accuracy in diagnosis of the observation target becomes lower.